There are keyboards with hall-effect/magnetic switches that allow precise measurement of how much any given key is held down. With that said it’s be possible to map the signals from WASD to emulate a controller’s left stick (at least in games that allow simultaneous kb+m and controller inputs, but that’s fairly common in my experience).

I have a keyboard like that on pre-order and I’m definitely looking forward to trying it. 4mm of travel isn’t much, but it should still be better than a binary signal.